CMP polishing pads (or “CMP pads”) are components of CMP systems that polish, or “planarize,” surfaces. CMP is one step in manufacturing of many semiconductor and optical components. For example, CMP is an intermediate step in semiconductor wafer processing of electronic devices, where it is used to planarize the surface between processing steps.
CMP systems polish by the action of a CMP pad attached to a platen of a CMP system and a chemically abrasive slurry moving across the surface of a work piece. CMP pads can be made of one of a variety of materials, including thermoplastics or fabrics, in the form of solid surfaces, surfaces with grooves, or felts, and the slurries typically include abrasive particles in a chemical etchant. The CMP pad and work piece move relative to each other in a motion that is intended to ensure uniform polishing—usually in a complex motion combining rotation and orbiting. In addition, uniform polishing is accomplished by having the CMP system deposit fresh slurry and remove the slurry from the work piece.
CMP pads are disposable components that can be attached to the platen by an adhesive. Typically, CMP pads are provided to the CMP equipment user with either a pressure sensitive adhesive (PSA) or a thermoset, or heat-activated, adhesive. A PSA has a release liner over the adhesive that is removed prior to placing the CMP pad on the platen. The the thermoset adhesive is heated to activate the adhesive.
The PSA may be provided as a roll or sheet of film having the PSA on one side and a second adhesive on the back side. The fabrication of a CMP pad with a PSA and release liner is usually accomplished by lamination of the backside of the PSA film to the backside of a CMP pad material. Specifically, the CMP pad material and the PSA film with release liner are fed through the pinch rollers of a laminator. If the second adhesive is heat-actuated, then the pinch roller that presses against the PSA film is heated.
CMP pads can also be constructed of a CMP pad material and a “sub-pad” having different properties, such as different hardnesses or having conduits for the flow of abrasive fluids. These multi-layered CMP pads can be produced by laminating, in one step, the CMP pad material with a sub-pad having an adhesive on one side and a PSA film and release liner on the opposite side. Prior art methods of producing CMP pad supply the stack of CMP pad and any sub-pad material, along with the PSA film and release liner directly through the pinch rollers of a laminator.
There are several problems with this prior art method of laminating CMP pads. First, variations of the thickness of pads or sub-pads requires the adjustment of laminators, such as the gap between pinch rollers, to ensure the proper application of lamination pressure. Second, the contact of the CMP pad with the pinch rollers can damage or contaminate the front surface of the CMP pad material, especially if the rollers are made of incompatible material. For example, the rollers may physically damage the front surface of the CMP pad due to scratches on other imperfections which arise from normal wear of the rollers. Physical and chemical contamination of the work piece is of particular concern in the manufacturing of semiconductor wafers. Third, if the CMP pad surfaces are handled during laminating, the person laminating the CMP pad may damage or contaminate the pad. Fourth, non-uniformities in the laminated CMP pad, such as warping or curling, or bubbles, wrinkles, or uneven lamination in the PSA or sub-pad material can occur from improper distribution of the compressive pressure during lamination.
It would be desirable to produce a CMP pad with a PSA backing using a lamination method that overcomes the problems with prior CMP laminating methods. In particular, it would be desirable to have a method of laminating a CMP pad that does not warp or otherwise change the shape of the CMP pad, or contaminate the CMP pad. It is also desirable to have a method that allows for lamination of CMP pads with sub-pads, and that is usable for PSA films that attach to the CMP pad using either pressure or heat actuated adhesives.